Lignocellulosic biomass contains variable amounts of cellulose, hemicellulose, lignin and small amounts of protein, pectin, wax, potassium chloride and other inorganic compounds. Lignocellulosic biomass should be understood in its broadest sense, so that it apart from wood, agricultural residues, energy crops also comprises different types of waste from both industry and households. Cellulosic biomass is a vast poorly exploited resource, and in some cases a waste problem. However, hexoses from cellulose can be converted by yeast to fuel ethanol for which there is a growing demand. Pentoses from hemicellulose can not yet be converted to ethanol commercially but several promising ethanologenic microorganisms with the capacity to convert pentoses and hexoses are under development.
The production cost of fuel ethanol from lignocellulosic feedstocks is at present much higher than from starch/sugar feedstocks.
Until recently, the cost of cellulytic enzymes for conversion of the pretreated cellulosic feedstock to fermentable sugars has been prohibitive.
This cost has been dramatically reduced caused by the successful research work carried t by Novozymes and Genencor, sponsored by Department of Energy, USA.
More cost reductions are however needed to establish a commercially viable exploitation of the huge quantities of lignocellulosic feedstocks.